This invention relates generally to the field of materials construction and, more specifically, to a system and method for constructing a laminate.
Laminated Object Manufacturing (LOM) is a commercial rapid prototyping process that is used to fabricate industrial design prototypes directly from computer-aided design (CAD) files. In the LOM process, a CAD file is first generated of a solid model of the part to be fabricated. The CAD model is next xe2x80x9cslicedxe2x80x9d into a series of thin sequential layers. This CAD file is then sent to the LOM rapid prototyping unit to build a three-dimensional model of the part by a layered manufacturing approach.
The layered manufacturing approach is briefly described as follows. First, an automated sheet feeder mechanism transfers a single oversized ply of material (woven or tape) to a LOM build platform. A heated roller next bonds the ply to the build layer (the back of the ply typically contains a thermally activated adhesive). A laser then cuts the ply into the geometric shape that corresponds with the particular xe2x80x9cslicexe2x80x9d layer from the CAD file. Regions of the ply that do not correspond with the part volume are laser cross-hatched for subsequent removal. Successive ply transfer, lamination, laser cutting and cross-hatching steps are performed for each corresponding geometric xe2x80x9cslicexe2x80x9d layer from the CAD file until the entire object is constructed (which is now embedded in the cross-hatched volume of the ply stack). In a final decubing step, the laser cross-hatched regions of the lamination stack are manually removed to expose the three-dimensional model. The standard LOM process typically utilizes adhesive backed sheets of paper as a build material that produces three-dimensional models having properties close to that of wood.
The commercial LOM process described above (designated 2D LOM) has a major disadvantage for fabricating continuous fiber, curved composite structures in that the planar build technique does not allow the reinforcement to follow the direction of curvature of the component. This particular shortcoming of 2D LOM for composites fabrication has been overcome by the development of the curved LOM process (designated 3D LOM). In 3D LOM, a mandrel or tool is first generated by 2D LOM onto which the final part will be fabricated. The tool serves as the mold for producing the overall curved part geometry. The process is thus similar to conventional composites processing in that the laminate plies are sequentially draped over the surface of a tool and compacted with a flexible, elastomeric heated diaphragm. In recent years, special LOM tape formulations have been produced that allow fabrication of parts from a variety of metal, ceramic, polymer and composite materials. The advantages of LOM for fabricating composite components is based on its inherent capability for handling sheet materials, its high degree of automation, and the additional benefit that the process requires no tooling (other than the mandrel which it generates).
For parts fabricated with materials that require low lamination temperatures, standard LOM paper is often adequate as a build material for the mandrel/tool. However, for laminating tapes, plies, or prepregs that require higher lamination temperatures and/or compaction pressures, alternate materials for the mandrel/tool are required. The time, cost, and technical development required for fabricating such a mandrel/tool from these materials can equal that of the desired part. These tooling requirements of 3D LOM make the process less attractive as an effective rapid prototyping technique, especially for rapid composites prototyping. A rapid method for generating the required mandrel/tool shape is needed to make 3D LOM a more viable rapid prototyping process. In addition, a rapid method for generating composite parts with complex curvature is needed to enhance and extend the capabilities of 3D LOM.
Another rapid prototyping technique utilizes reconfigurable tooling (RT). A reconfigurable tool typically consists of an array of discrete, moveable metal pins whose cross-sectional geometry can vary depending on the particular forming application. The reconfigurable tool is interfaced with a computer software algorithm to allow the rapid repositioning of the discrete pins to generate a range of tooling surfaces. Usually an elastomeric interpolating layer is placed between the reconfigurable tool surface and the material to be formed to eliminate part dimpling caused by the die pins. This interpolating layer produces a smoother tool surface contour. Initially, RT was utilized for rapid prototyping for sheet metal parts. In recent years, however, RT has been developed that allows fabrication of parts from a variety of metal, ceramic, polymer and composite materials. The advantage of RT for fabricating composite components is based on its inherent capability for forming sheet materials and its high degree of automation. An RT concept is needed as a rapid method for generating composite parts with complex curvature to enhance and extend the capabilities of both composites forming and LOM-based prototyping technology.
While these systems and methods have provided a significant improvement over prior approaches, the challenges in the field of materials construction have continued to increase with demands for more and better techniques having greater flexibility and adaptability. Therefore, a need has arisen for a new and rapid system and method for constructing a laminate.
In accordance with the present invention, a system and method for constructing a laminate is provided that substantially eliminates or reduces disadvantages and problems associated with previously developed systems and methods.
A system for constructing a laminate is disclosed. The system comprises a ply feeder that sequentially stacks one or more plies to form a ply stack. A computer directs a laser to cut each ply to a desired shape after becoming part of the ply stack. The ply stack is then placed on a reconfigurable tool. An applied pressure compresses the ply stack against the reconfigurable tool while an actuator, or actuators, subsequently reconfigures the reconfigurable tool elements to a predetermined shape. In a more particular embodiment, a composites forming process is used, such as diaphragm forming, to compress the ply stack before the reconfigurable tool elements are reconfigured.
A method for constructing a laminate is disclosed. The method comprises four steps. Step one calls for utilizing a laminated object manufacturing process to lay-up a stack of plies to create a ply stack. Step two requires positioning the ply stack on a reconfigurable tool. Step three calls for compressing the ply stack against the reconfigurable tool, and the last step calls for configuring the reconfigurable tool to a desired shape. In a more particular embodiment, additional steps provide for placing the ply stack between two resilient diaphragms and compressing the ply stack before the step of configuring the reconfigurable tool to a desired shape.
A technical advantage of the present invention is the rapid generation of LOM mandrels/tools suitable for high temperature materials processing, such as 3D LOM of composites. The time and cost of developing and fabricating these high temperature tools traditionally can equal that of the actual structure being constructed.
Another technical advantage of the present invention is the ability to utilize LOM and RT to fabricate composite structures with complex curvature. The advantages of LOM for fabricating composite structures is based on its inherent capability for handling sheet materials, its high degree of automation, and the additional benefit that the process requires no permanent tooling. The advantage of RT for fabricating composite structures is based on its inherent capability for forming sheet materials and its high degree of automation.
An additional technical advantage of the present invention is extending the capabilities of composites forming, resulting in a greater range of complex designs and shapes with a LOM-based laser cutting and darting step before the final forming process. The automated laser cutting and darting step before final forming minimizes wrinkling and distortion of the material during forming.